Priority is claimed to Japanese Patent Application Number JP2004-040883 filed on Feb. 18, 2004, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a circuit device of a hollow structure with a semiconductor element housed in a casing thereof.
2. Description of the Related Art
A description is given of a constitution of a conventional circuit device 100 with reference to FIGS. 10A and 10B. FIG. 10A is a plan view of the circuit device 100, and FIG. 10B is a cross-sectional view thereof (see Patent Literature 1).
Referring to FIGS. 10A and 10B, a land 102 made of a conductive material is formed in the center of the circuit device 100, and around the land 102, one end of each of a number of leads 101 is in close vicinity thereof. The one end of each lead 101 is electrically connected to a semiconductor element 104 through a thin metal wire 105, and the other end is exposed from a sealing resin 103. The sealing resin 103 has a function to seal the semiconductor element 104, land 102, and leads 101 and to integrally support the same. In the case of employing an optical element as the semiconductor element 104, light transparent resin is employed as the sealing resin 103.
As the method of sealing the circuit element such as a semiconductor element, there is a method other than resin sealing. An example thereof is a sealing method in which a casing including an internal space is formed of a metal or resin material and the circuit element is incorporated in this internal space. Patent Literature 1: Japanese Patent Laid-Open publication No. 11-340257
However, in the case where an element emitting and receiving short-wavelength light is employed as the aforementioned semiconductor device 104, many problems are caused. Specifically, such problems include a case where short-wavelength light adversely affects the sealing resin 103 and a case where a light signal is degraded by sealing resin. In the former case, when an element emitting and receiving short-wavelength light (for example, blue laser light with a wavelength of about 405 nm) is employed as the semiconductor element 104, color change or the like is caused in the sealing resin 103 by that light. In the latter case, the sealing resin 103 with a release agent and the like mixed therein is not transparent enough, and the short-wavelength light such as blue laser light emitted and received by the semiconductor element 104 is attenuated.